“Watch out for false prophets. They come to you dressed like sheep, but inside they are vicious wolves.
References for Matthew 7:15
You will know them by their fruit. Do people get bunches of grapes from thorny weeds, or do they get figs from thistles?
In the same way, every good tree produces good fruit, and every rotten tree produces bad fruit.
A good tree can't produce bad fruit. And a rotten tree can't produce good fruit.
Every tree that doesn't produce good fruit is chopped down and thrown into the fire.
Therefore, you will know them by their fruit.